In many cases, vinyl chloride resins are used as a vinyl chloride resin composition in which a plasticizer is added in order to not only apply various performances such as flexibility, but also decrease working temperatures in various molding processes such as extruding or calendaring, thereby facilitating the molding processes.
It is desirable that the plasticizer used in such a vinyl chloride resin composition has performances of having excellent compatibility with vinyl chloride resins and providing a molded article of a vinyl chloride resin composition having excellent heat resistance and freeze resistance.
In the related art, as the plasticizer used in the vinyl chloride resin composition, a higher alkyl ester of a polybasic acid such as a phthalic acid diester, an adipic acid diester, or a trimellitic acid triester has been known, for example. In the related art, the phthalic acid diester is mainly used in many cases, by considering a price or a balance between performances of heat resistance and freeze resistance, but in recent years, the trimellitic acid triester has been used as the plasticizer, in the case where higher heat resistance is required. Specifically, the trimellitic acid triester such as tri-2-ethylhexyl trimellitate (hereinafter, abbreviated as “TOTM”), triisononyl trimellitate (hereinafter, abbreviated as “TINTM”), or triisodecyl trimellitate (hereinafter, abbreviated as “TIDTM”) has excellent compatibility with vinyl chloride resins, and even in the case where a molded article obtained by using a vinyl chloride resin composition including the trimellitic acid triester is exposed in a heating environment, the mass thereof decreased is small (excellent heat aging resistance is obtained). Thus, the trimellitic acid triester is frequently used for heat resistant wires used at a temperature equal to or higher than 105° C. or dashboards for a car.
However, in recent years, the demand for freeze resistance or heat resistance becomes increasingly stronger, and it has been difficult to apply sufficient freeze resistance or heat resistance to a molded article by using the TOTM, the TINTM, and the TIDTM.
As the plasticizer for obtaining a vinyl chloride resin composition with which a molded article having excellent heat resistance and freeze resistance is obtained, for example, a plasticizer which is an esterified product of trimellitic acid and an aliphatic alcohol having 9 carbon atoms and in which a linear aliphatic alcohol and a branched aliphatic alcohol are used at a specific ratio as the aliphatic alcohol, has been known (for example, see PTL 1). However, the plasticizer has poor compatibility with vinyl chloride resins. Accordingly, the plasticizer bleeds out on a surface of a molded article obtained from a composition including the plasticizer and a vinyl chloride resin over time, and as a result, a problem regarding deteriorations in heat resistance and freeze resistance of a molded article over time is raised.
A polyester-based plasticizer has also been known as the plasticizer for obtaining a molded article of vinyl chloride resins. As the plasticizer for obtaining a molded body having excellent freeze resistance, specifically, a plasticizer with which flexibility of a molded body can be maintained even at a low temperature, a plasticizer obtained by causing a reaction between a glycol having a branched aliphatic structure, a cyclic ester having 3 to 18 carbon atoms or an aliphatic oxycarboxylic acid having 3 to 18 carbon atoms, a dibasic acid such as adipic acid, and a monoalcohol having 2 to 22 carbon atoms has been known (for example, see PTL 2). However, even in the case where the plasticizer disclosed in PTL 2 was used, it was difficult to apply sufficient freeze resistance to a molded article.